BABIES AND THEIR FEET
First a little about Human Development
Human developmental history is important because it gives the podiatrist/chiropodist clues to the neuromuscular maturity of the child. Development occurs in an orderly sequence (head control to mature walking). A significant deviation from the norm could indicate the possibility of a lower extremity musculoskeletal or neuromuscular disorder.
Principles of Human Development
Human development is a continuous process from conception to maturity (beginning in utero). The sequence is the same for all children, but the rate of development may vary. It is intimately related to the maturity of the nervous system. Over time, gross uncoordinated movement is replaced by fine coordinated movement. Development is ‘cephalocaudal’. The first step towards walking is development of head control. Primitive reflexes must be lost before voluntary movement is acquired.
Some Developmental Milestones
Gross Motor Skills
Baby has incomplete head control.................1 month
Baby rolls over…………………………………4 months
Baby sits without support……………………..6 months
Baby is crawling……………………………….9 months
Baby can lift him/herself upright……………..9-10 months
Toddler can walk with some help…………….11-12 months
Toddler can walk unassisted…………………12-15 months
Toddler has a stable gait……………………....24 months
Child has heel-to-toe gait pattern…………….3-4 years
Child can balance on one foot………………..3-5 years
Fine Motor Skills
Baby fixes both eyes on light………………….1 month
Baby brings objects to mouth…………………4 months
Baby picks up objects…………………………..6 months
Baby feeds with finger…………………………7 months
Baby develops a pincer grip…………………..9 months
Toddler follows simple commands…………...12 months
Toddler spoon feeds………….………………..15 months
Toddler shows hand preference……………...21months
Social/Emotional/Language
Smiles begin……………………………………1-2 months
Laughing…………………………….………….4 months
Babbling………………………………………...6 months
Says Dada/Mama……………………………....8 months
Anxiety of strangers…………………………....9 months
Understands NO……………………………….10 months
Separation distress…………………………….12 months
Independence………………………………….18 months
Puts two words together………………………2 years
Cooperative play……………………………….3 years
Before Birth - Intrauterine Growth and Development
An infant is considered full term from 38- 40 wks. Development is measured from conception. Gestation is divided into two stages: Embryonic (tissue & organ differentiation), 0-8 weeks and Fetal, 8 weeks to birth. The length of the foot is sometimes used as an indicator of fetal age. For clinical use gestation is divided into 3 monthly trimesters.
Development of the lower limbs in the fetus: Limb buds appear at 4 weeks. After 4 to 8 weeks (the most critical & vulnerable period due to rapid cell division & tissue differentiation), limb buds are composed of 2 types of tissue: the mesoderm which gives rise to bones, muscles, tendons & ligaments AND the ectoderm which gives rise to skin, nails, glands Nerves and blood vessels sprout from main trunk. Limbs develop proximal to distal (from top to bottom).
During the 5th week limb bud segmentation takes place with the terminal segment being the precursor to the foot. The foot develops with appearance of the rear-foot, then the mid-foot area and finally the toes. In the 6th week the skeleton starts to develop from from mesenchyme tissue and becomes cartilage.
There are several factors that influence growth during this time? They are gender, genetics, congenital diseases (such as CDH, Spina bifida), maternal disorder (such as diabetes, pre-eclampsia), hormones, socioeconomic & environmental factors, illness, teratogenic agents (during the 1st trimester) and bone tumours.
At Birth
The infant is temporarily in a physiological flexed position due to the cramped uterine position. Limbs will resist passive extension, head control is not present and the infant relies on reflexes not on the higher brain centres for motor control.
Birth to Four Months
By 4 to 6 weeks the infant begins to smile and at 8 weeks begins to vocalise. By the end of 4 months head control is achieved in both the supine, prone and upright positions. Head control is the most important preliminary developmental milestone. Weight shifting, along with reaching in the prone position is achieved at about 4 months.
Four to Eight Months
The shoulder and pelvis can rotate independently, allowing segmental rolling. This allows for sitting, standing, and reciprocal arm and pelvic swing during gait. The most important achievement is independent movement of the limbs from the head position. This allows for sitting and crawling. Also at this time the baby may be able to laugh out loud.
Eight to Twelve Months
The baby is usually able to crawl by nine months. The toddler is able to pull itself up onto its knees and eventually be able to stand. During this time the toddler also walks holding onto furniture (cruising) and responds to words and questions.
Twelve to Fifteen Months
Appearance of independent early walker gait (plodding gait-not heel-to-toe until age of 3 yrs.). At 15 months -can kneel without support and creep upstairs
Growth of the Foot
Prior to Birth
The fetus’s foot is triangular in shape. The tarsus (ankle bones) is 40% of foot length, which changes in proportion & shape with growth allowing for bipedal gait. In the 3rd trimester the fetal position, lower limbs are folded with one leg crossing the other at the ankle, feet inverted & plantarflexed.
At Birth (Congenital)
The following bones are visible at birth: talus (an important bone that connects the leg to the foot), calcaneus (heel bone), cuboid, metatarsals, and most toes (phalanges)
At birth the foot is mainly cartilaginous prior to complete ossification (when cartilage becomes bone). The foot is therefore malleable allowing for some degree of correction when a deformity is present.
Ossification of the Foot After Birth
As mentioned before, ossification is the process in which bone is formed from cartilage. Condensed mesenchyme tissue is replaced by cartilage (endochondral ossification). Linear growth of long bones is by cartilage cell division. Center of a bone shaft is invaded by osteoblasts (bone building cells) - the primary centre of ossification. Bone is generated progressively outward from this centre.
In the 7th week ossification begins with the appearance of the primary centre in the femur (thigh bone). In the 9th week the bones of the foot begin to ossify beginning with the metatarsal bones (the long bones) connecting the toes.
All ossification centres are present at birth. Shafts (diaphyses) of long bones are ossified at birth, but the epiphyses (ends of the long bones) are mostly cartilaginous (soft). The diaphysis and epiphysis are separated by the epiphyseal growth plate which is an area of postnatal growth of long bone. At birth secondary centres of ossification appear in the epiphysis. Cartilage cell division in the epiphyseal plate occurs. Most active growth plates are those close to the knee. At puberty, the plates narrow as cartilage production slows and osteoblasts invade. Closure of growth plates follow a sequence related to the bone age of the child. It is interesting to note that the onset of an adolescent growth spurts often occur first in the foot.
So what lower limb bones do we not have at birth? Lateral Cuneiform – shows up around 1st year, Medial Cuneiform - shows up around 2nd year, Intermediate Cuneiform – shows up around 3rd year, Sesamoids (including patella) – around 3rd year, and the Navicular - around 3rd year.
And what lower limb skeletal structures do we not have at birth? These are acetabulum, the femur head, the cuboid, the malleoli, the fibula head and the greater and lessor trochanters.
Part 2 will be a summary table of osseous (bone) development of the lower limb.
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